A system capable of presenting a speed with unnecessary acceleration and deceleration being suppressed is named as a system for reducing consumption energy when driving a vehicle. Patent Document 1, as a method of reducing consumption energy, calculates a speed to pass through without stopping at a traffic light utilizing information such as an aspect indication schedule of the traffic light, and presents this to encourage a driver to perform energy-efficient driving.
An object of the above system is to allow passing through a road intersection without stopping: by calculating, at a site P which is a predetermined distance D short of a road intersection provided with the traffic light, and based on signal state information (schedule of green light and red/yellow light) of the road intersection, the distance D, allowable maximum speed information between the site P and the road intersection, and time of arrival at the site P, recommended time required and a recommended driving speed between the site P and the road intersection to pass through the road intersection during the green light; by indicating or transmitting the recommended driving speed to the vehicle; and by having the vehicle drive to the road intersection at the recommended driving speed.
It should be noted that Patent Documents 2 and 3 are disclosed as techniques pertinent to the present invention.